1. Field of the Invention
The present invention relates to trays for compost used in the cultivation of mushrooms.
2. Description of the Prior Art
The growth of mushrooms takes place in several stages requiring different ambient conditions. In the first stage, the trays are filled with raw compost and then placed in a pasteurization room and held at an elevated temperature for a number of days. In the second stage, the trays are dumped and then refilled with the pasteurized compost to which spawn has been added, and then placed in a room which has closely controlled humidity conditions for a number of days for the growth of mushrooms.
The mushrooms may be picked from the trays in the growing room which is dark and humid or the trays may be moved out of the growing room, picked and then restacked in the growing room.
As can be readily understood, the growth of mushrooms at a large mushroom farm requires the use of thousands of trays in which the compost is pasteurized at high temperatures, the room system is germinated under controlled conditions and the mushrooms are grown under controlled humidity and temperature conditions. These trays must be stackable in close relationship, in order to accommodate the greatest possible number within the enclosed areas, and the trays must be strong enough to withstand the strain of being transported by fork-lifts and conveyor belts and/or rollers from one area to another.
The cost of wooden mushroom trays has increased substantially in recent years and such wooden trays have a useful life of only about three years, on the average, so that their cost per year is fairly high. Wood deteriorates rapidly under the varying conditions of use so that wooden trays break under the strain of transportation or under the weight of stacking. Wood also expands to a substantial degree when moved from a dry atmosphere to a wet atmosphere, and in some instances, where stacks of wooden trays are placed in touching relation, the expansion of the wooden trays is sufficient to topple the outermost stacks.